Synthesis of amines



2,017,069 T741411; 2.1/6- Qj 11mg XvoYBk/ UNITED STATES PATENT OFFICESYNTHESIS OF AMINES Wilbur A. Lazier, Wilmington, DeL, assignor to E. I.du Pont de Nemours & Company, Wilmington, Del., a corporation ofDelaware No Drawing. Application February 6, 1931,

Serial No. 514,055

22 Claims. (Cl. 260127) This invention relates to an improved catalyticprocess for causing dehydration reactions to take place with organichydroxy compounds. More particularly the invention relates to animproved process for the synthesis of amines.

Active carbon has been used extensively as an absorbent and decolorizingagent but only a limited use has been made of active carbon impregnatedwith inorganic materials. As an insynthesis. The higher alcohols,however, tend to form olefines by dehydration and these do not reactwith ammonia to form amines to any appreciable extent, and therefore thedehydrating side reaction must be suppressed. In my improved process foramine synthesis both the tendency towards dehydrogenation of thealcohols to form aldehydes and hydrogen and the tendency of the higheralcohols to dehydrate to unsatustance of such a use there may bementioned rated hydrocarbons are suppressed. This latter 1 theutilization of active charcoal impregnated suppression does not occur,however, when amwith copper oxide for gas adsorption. Carbon, monia orother bases are absent.

or carbon impregnated with any inorganic ma- The carbon, which forms thesupport for the terial as herein disclosed, has not, in so far asdehydrating agent, should have a rigid porous -15 I am aware, beenheretofore employed for the structure and should preferably contain nomore 15 direct synthesis of amines, or for any other pureash (inorganicmaterial) than is normally found ly dehydration reaction. in the bestcommercially available active carbon, This invention has as an object aprocess for about 1% to 5%. In carrying out my invention effecting adehydration reaction with organic hy- I prefer to use an active carbonprepared by droxy compounds with substantial or total supthe combustionof wood, preferably hard wood, pression of dehydrogenation. which yieldsa charcoal of relatively low ash con- Another object is an improvedprocess for the tent and high activity. The activity of the chardirectsynthesis of amines. Other objects will coal is improved by heating athigh temperatures appear hereinafter. in the presence ofoxygen-containing gases, su- These objects are accomplished by thefollow perheated steam, chlorine or other activating 25 ing invention,which in its general aspects, comagents. This charcoal, after treatmentwith a prises passing a vapor or a vapor mixture consuitable dehydratingoxide, is1 ltileated to a suittaining the organic hydroxy compound orcomable reaction tempera ure an e orgamc compounds to be dehydrated overa heated catalyst pound or mixture containing organic compoundscomprising active carbon and a suitable dehyin vapor form is passed overthe heated catalyst. 30 drating agent, preferably a dehydrating metal-Thus in the synthesis of amines a vapor mixture lic oxide. of ammoniaand an alcohol reacts withfthe elimi- In the synthesis of amines, areaction with nation of water and the formation 0 primary, which theapplication of the present invention secondary and tertiary amines. Fora more deis especially concerned, a vapor mixture of an taileddescription of the methods by which my 35- alcohol and ammonia, or3111.! amino compound invention may be practiced, refeil'fnce gmay 3ehaving at le one r a ive y l gen atom athad to the following exampleswhic are ven y h d o ni r n. is Passed Over my pr v way of illustrationand not as limitation. catalyst at an elevated temperature.- In the l Vsynthesis of amines from alcohols and ammonia, ramp e 40 or in synthesesof like character, it is desirable 0 -h dr d and twenty-five cc. ofactivated to use a catalyst which will produce substantial charcoalweigmng grams and having an h fgz f z g? g gg g g g gi g content of1.1%, the alkalinity of which was 0.3% calculated as sodium, was heatedfour hours at 45 tendency for the alcohol to dehydrogenate to andexhausted at a pressure of less than 45 alflehyde and hyqmgen instead Qto dehydrate 5 mm. After cooling to room temperature in a with theammoma to form amines. In addlm carbon was covered with 125 cc tlonthere is the possibility of a competitive devacuum 6 hydration reactionnot involving the ammonia or contammg grams of med and leading to theformation of ethers or unammmum nitrate per 100 After allowing 50saturated hydrocarbons.. In the synthesis of to stmd 2; g 35 2 figs?methyl amines, where the ether is the only cornwas @0811 e 0 an 8 Car 11e pound that can be formed by this reaction, the It was then heated inIOOSEIY Covered Vessel di'fliculty is not serious since dimethyl etheris at 400 C. for two hours in order to convert 55 the equivalent ofmethanol for the methyl amine the aluminum nitrate into aluminumoxide... Ait- 55 er the impregnating process, the alumina content was4.3%.

In employing this catalyst for the synthesis of butylamine. 50 cc. wasloaded into a tube furnace which was heated to 325 C. and a mixture ofthe vapor of normal butanol and ammonia was passed over the catalyst atthe rate of 40 cc. of liquid butanol and 23 grams of anhydrous ammoniaper hour. After a four-hour run the excess ammonia. was removed from theproduct by boiling through an efllcient fractionating column and theproduct analyzed by fractional distillation. It was found that thecondensate contained, in addition to a quantity of unconverted butanol,mono-, di-, and tributylamines, corresponding to a 5.3% conversion tomonobutylamine and a 14.5% conversion to the diand triamines, or a totalconversion to butylamines of 19.8%. Gas losses caused by thedehydrogenation of the alcohol and the formation of butane and butyleneamounted to about 3.0%.

Example 2 Fifty cc. of activated charcoal prepared from hard wood wassoaked for eight hours in a solution of aluminum nitrate containing 14g. of alumina per 100 cc. The charcoal was drained, dried, and ignitedin a loosely covered vessel for two hours at 450 C. After cooling, thecatalyst mass containing about 11% of A120: was charged into a tubefurnace and maintained at a temperature of 325 C., while a mixture ofnormal butanol vapor and ammonia was passed over it. The time of contactof the gaseous mixture with the catalyst was about 2.4 seconds and theammonia-butanol ratio 2.5. Distillation of the product showed that 46.7%of the butanol had been converted to butylamines of which 17.9% had goneto form monobutylamine and the remainder, the diand triamines. Gaseousdecomposition of the alcohol to butane, butylene, and hydrogen amountedto about 4% of the butanol passed over the catalyst.

Example 3 A catalyst containing thoria on charcoal was prepared byoutgassing at 400 in a vacuum a sample of activated wood charcoalcontaining between 1 and 2% ash and impregnating with an equal volume ofa solution containing 20 g. of crystallized thorium nitrate per 100 cc.After drying, the impregnated carbon was ignited to convert the thoriumnitrate to oxide. When employed for the synthesis of butylamines underthe conditions described in Example 2 above, this catalyst gave a totalconversion of the butanol to amines of 41%, of which 32% was a mixtureof the diand triamines. The gas consisted almost wholly of hydrogen incontradistinction to the formation of butylene and butane usuallyobserved when an alumina-oncharcoal catalyst is employed.

Example 4 An alumina supported on charcoal catalyst prepared exactly asdescribed in Example 1 above was employed for the continuous gas phasesynthesis of methylamines from a mixture of methanol and ammonia. Fiftycc. of the alumina-impregnated charcoal was heated at 340 C. while equalmoles of ammonia and methanol were passed over it. The rate of flow was25 cc. of alcohol per hour with the corresponding amount of ammonia. Thetotal conversion to 'in any other suitable way.

amine. The simultaneous formation of dimethyl 5 ether amounted to aboutof the methanol passed, with practically no decomposition to hy drogen,formaldehyde, or oxides of carbon.

Example 5 One liter of a 6-14 mesh alumina-impregnated activatedcharcoal containing 8.4% A120: was loaded into an extra heavy aluminumlined tube. The mass was heated to 328 C. while a mixture of normalbutanol vapor and ammonia was pumped over it at 200 lbs.-pressure. Therate of alcohol flow was about 500 cc. per hour and the molecular ratioof ammonia to butanol about 1.5. Forty-five per cent of the butylalcohol was converted to amines, the distribution being about 17% tomonobutylamine, about 22% to dibutylamine, and about 6% totributylamine. Gas production amounted to less than 8% of the alcoholpassed thru the system.

A large variety of active carbons may be used 25 for the preparation ofthe impregnated catalyst, provided the ash is of sufficiently lowconcentration and does not contain undesirable constituents. Thesecarbons may be prepared synthetically as by dehydration of furfural orcarbohydrates or by combustion processes. I prefer to use wood charcoal,but that obtained from nut shells is also suitable. Active carbon aswell understood by those skilled in the art, refers to carbon having agreatly increased surface extension due to its high degree of porosityas compared to ordinary or inactive carbon.

Among the various methods used for the production of active carbon theremay be mentioned the treatment of the carbon with steam at about 900 C.which oxidizes the hydrocarbons within the charcoal thereby leaving itin a highly porous and more active state.

A variety of methods may be used for the preparation of the impregnatedcharcoal such as treating the charcoal with a soluble salt of the metalfollowed by a precipitating agent, or soaking the charcoal in acolloidal solution or Preferably I use the vacuum impregnation methodclaimed in application, Serial No. 470,219, filed July 23, 1930 by H. R.Arnold and myself.

In addition to the alumina and thoria mentioned in the examples, othersuitable catalytic dehydrating agents such as titania or various saltsand certain rare earth oxides, may also be used. Various phosphates andsulfates have been found to give small, though definite conversions. Insome instances an agent may cause a high conversion of one lacohol intothe corresponding amine while yielding a much less satisfactoryconversion for another alcohol. Thus, aluminum phosphate or sulfate,while causing a high conversion of methanol to methylamines. is lesssuitable for the production of butylamines.

It is to be understood, however, that the novelty of the presentinvention resides in the discovery of the advantages resulting from theuse of a catalyst comprising any suitable dehydrating agent mounted onan active carbon support as herein described, rather than in theselection of a particular dehydrating agent to be used with my improvedcarbon support. The percentage of oxides used on the surface of thecarbon support may vary over wide limits. For example,

from 1 to 10% of alumina on the charcoal may be used. but I prefer touse about 7%.

The conditions or conducting the reaction with my improved catalyst maybe widely varied. Temperatures or about 325 C. have been indicated inthe examples, but these may be varied as the individual case permits.Rates of flow may also be varied over a. wide range. Ammonia. ispreferably used in excess of the amount the oreticaily required to reactwith the alcohol, but this, too, is not a rigid requirement. My im--proved catalysts are applicable when the process is conducted atordinary, reduced, or superatmospheric pressures. In the case of thehigher boiling alcohols, it may be desirable to conduct the process in apartial vacuum, while for the more volatile alcohols, increase in timeof contact is gained through the use of pressure.

The impregnated carbon catalysts set forth herein may be employed forthe direct synthesis of aliphatic and aromatic amines. For example, theyare suitable for the preparation from methanol and ammonia of thevarious methyl-amines and for other aliphatic amines from ammonia andthe corresponding alcohols such as ethyl-l amines, propylamines,butylamines, hexylamines,

and laurylamines. This particular catalyst, however, is especiallyuseiul for the synthesis of amines having more than one carbon atom inthe alkyl group inasmuch as the tendencies of the alcohols to dehydrateto hydrocarbons are suppressed. Aromatic amines may be produced in thesame manner as the aliphatic amines by using aromatic hydroxy compoundsinstead of aliphatic alcohols. Thus, a mixture of ammonia and phenolyields aniline. Secondary, tertiary, or

mixed amines having different alkyl groups mayalso be produced byreacting a primary or secondary amine with an alcohol. The presentprocess is useful for the alkylation of aromatic amines; for example, inthe conversion of aniline to ethyl aniline by reacting aniline withethyl alcohol. Amino compounds of polyhydric alcohols, such as glycerol,may be prepared by reacting the polyhydric alcohol with ammonia or anamine. My improved process for synthesizing amines includes, therefore,the reaction of amino compounds containing at least one reactivehydrogen atom attached to nitrogen with alcohols. The term amino" asused herein in connection with the material passed over the catalystrefers therefore to a compound having an NH: or NH group, and includesprimary and secondary amines. Ammonia, or course, may be used in placeof the amino compound. Thus, primary, secondary and tertiary amines maybe produced by my improved process.

While my improved process is especially valuable ior the production ofamines, it is to be understood that in its broadest aspect the inventioncomprises the dehydration of organic hydroxy compounds for theproduction of dehydration products without the concomitant production ofdehydrogenation products in undesirable amounts. Among the manydehydration reactions which may be carried out 'by my invention are thefollowing: The dehydration of a mixture of alcohol and acid for theproduction of an ester, as for instance the formation of ethyl acetatefrom ethyl alcohol and acetic acid; the conversion of alcohols to thecorresponding ethers, as for instance, methyl ether from methyl alcohol;the production in the absence of ammonia o1 oleflnes from the higheralcohols; the dehydration of an acid for the production of an anhydride,as for instance acetic anhydride from acetic acid; and the formation ofinner anhydrides, as for example the dehydration of an acid moleculesuch as acetic acid for the production or ketq'tie. For the purpose ofthe present invention ethers, (alcohols having the hydrogen of thehydroxyl group replaced by an alkyl group), may be considered assubstituted alcohols or hydroxy compounds. Thus, dimethyl ether andammonia, may by means of my improved catalyst, be made to react to formmethyl amines.

My improved process may be used with advantage because of the highconversion to amines obtained. In addition, the catalysts used in thepresent invention are especially valuable because of the low losses toside products obtained by their use. For example, in the conversion ofbutyl alcohol to butylamine by the ordinary catalysts, very high lossesto gaseous products are yielded a total conversion to amines of only12.6%

as compared to the 19.8% obtained with the alumina impregnated carboncatalyst.

The practice of the present invention is especially advantageous inconnection with the synthesis oi' butylamines because the synthesis ofthese amines in prior processes have offered difliculties notencountered in methylamine synthe-- sis. Thus, while methanol isdehydrated only to dimethyl ether, which is reactive with ammonia.butanol is subject to dehydration to butylene over the catalystsheretofore employed.

As many apparently widely diflferent embodiments of this invention maybe made without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in the appended claims.

I claim:

1. A process for producing amines which com- I prises passing the mixedvapors of a compound selected from the group consisting of alcohols andphenols and a compound selected from the group consisting of ammonia andamino compounds having at least one hydrogen atom attached to nitrogenover a heated catalyst comprising essentially a catalytic dehydratingagent supported on activated carbon.

2. The process of claim 1 in which the temperature is maintained betweenabout 325 C. to about 340 C.

3. A process for producing amines which comprises passing the mixedvapors of a compound selected from the group consisting of alcohols andphenols and a compound selected from the group having at least onehydrogen atom attached to nitrogenover a heated catalyst comprisingessentially a dehydrating metal oxide supported on activated carbon.

5. The process of claim 4 in which the temperature is maintained betweenabout 325 C. to about 340 C.

6. A process for producing amines which comprises passing the mixedvapors 01' a compound selected from the group consisting of alcohols andphenols and a compound selected from the group consisting of ammonia andamino componds having at least one hydrogen atom attached to nitrogenover heated activated charcoal impregnated with alumina.

7. A process for producing amines which comprises passing the mixedvapors of an alcohol and a compound selected from the group consistingof ammonia and amino compounds having at least one hydrogen atomattached to nitrogen over a heated catalyst comprising essentially acatalytic dehydrating agent supported on activated carbon.

8. A process for producing amines which comprises passing the mixedvapors of an alcohol and a compound selected from the group consistingoi ammonia and amino compounds having at least one hydrogen atomattached to nitrogen over a heated activated charcoal impregnated with acatalytic dehydrating agent.

9. A process for producing amines which comprises passing the mixedvapors of an alcohol and a compound selected from the group consistingof ammonia and amino compounds having at least one hydrogen atomattached to nitrogen over a heated catalyst comprising essentially adehydrating metal oxide supported on activated carbon.

10. A process for producing amines which comprises passing the mixedvapors of. an alcohol and a compound selected from the group consistingof ammonia and amino compounds having at least one hydrogen atomattached to nitrogen over heated activated charcoal impregnated withalumina.

11. A process of producing amines which comprises passing the mixedvapors of an alcohol and ammonia over a heated catalyst comprisingessentially a catalytic dehydrating agent supported on activated carbon.

12. A process of producing amines which comprises passing the mixedvapors of an alcohol and ammonia over heated activated charcoalimpregnated with a catalytic dehydrating agent.

13. A process of producing amines in which the mixed vapors of analcohol and ammonia are passed over a heated catalyst comprisingessentially a dehydrating oxide supported on activated carbon.

14. A process of producing amines which comprises passing the mixedvapors 01 an alcohol and ammonia over heated activated charcoalimpregnated with alumina.

15. A process of producing amines which comprises passing the mixedvapors of an aliphatic alcohol and ammonia over a heated catalystcomprising essentially a catalytic dehydrating agent supported onactivated carbon.

16. A process oi producing amines which comprises passing the mixedvapors of an aliphatic alcohol and ammonia over heated activatedcharcoal impregnated with a catalytic dehydrating agent.

17. A process of producing amines which comprises passing the mixedvapors of an aliphatic alcohol and ammonia over a heated catalystcomprising essentially a dehydrating metal oxide supported on activatedcarbon.

18. A process of producing amines which comprises passing the mixedvapors of an aliphatic alcohol and ammonia over heated activatedcharcoal impregnated with alumina.

19. A process for producing butyl amines which comprises passing themixed vapors of a butyl alcohol and ammonia over heated activated carbonimpregnated with a catalytic dehydrating agent.

20. A process for producing butyl amines which comprises passing themixed vapors of a butyl alcohol and ammonia over heated activatedcharcoal impregnated with alumina.

21. A process for producing methyl amines which comprises passing themixed vapors of methyl alcohol and ammonia over heated activated carbonimpregnated with a catalytic dehydrating agent.

a 22. A process for producing methyl amines which comprises passing themixed vapors of methyl alcohol and ammonia over heated activatedcharcoal impregnated with alumina.

WILBUR A. LAZIER.

CERTIFICATE OF CQRRECTION.

Patent No. 2,017,069. October 15. 1935.

WILBUR A. LAZIER.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows: Page 3,second column, line 5, for "ketone" read ketene; and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Office.

Signed and sealed this 17th day of December, A. D. 1935.

Lesl ie Frazer (Seal) Acting Commissioner of Patents.

